Review of Carbon Emission
Factors in the UK
Greenhouse Gas Inventory
Baggott SL
Lelland A
Passant NP
Watterson J
November 2004
This work forms part of the Global Atmosphere Research Programme of the
Department for Environment, Food and Rural Affairs.
=
Title
Review of Carbon Emission Factors in the UK
Greenhouse Gas Inventory
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Department for Environment, Food and Rural
Affairs
Customer
reference
RMP/2106
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Review of Carbon Emission Factors
2 November 2006
AEA Energy & Environment
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ii
=
Units and conversions
Emissions of greenhouse gases presented in this report are given in Million tonnes
(Mt) and kilotonnes (kt). To convert between the units of emissions, use the
conversion factors given below.
Prefixes and multiplication factors
Multiplication factor
1,000,000,000,000,000
1,000,000,000,000
1,000,000,000
1,000,000
1,000
100
10
0.1
0.01
0.001
0.000,001
Abbreviation
1015
1012
109
106
103
102
101
10-1
10-2
10-3
10-6
Prefix
peta
tera
giga
mega
kilo
hecto
deca
deci
centi
milli
micro
1 kilotonne (kt)
=
1 Million tonne (Mt) =
103 tonnes
106 tonnes
=
1,000 tonnes
= 1,000,000 tonnes
1 Gigagramme (Gg)
1 Teragramme (Tg) =
=
1 Mt
1 kt
Symbol
P
T
G
M
k
h
da
d
c
m
µ
Conversion of carbon emitted to carbon dioxide emitted
To covert emissions expressed in weight of carbon, to emissions in weight of carbon
dioxide, multiply by 44/12.
Review of Carbon Emission Factors
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Executive Summary
=
ES.1
This report set out the results of a work programme to review and update the
carbon emission factors in the 2002 UK greenhouse gas inventory. This was
part of a wider programme of inventory review and improvement to prepare
the greenhouse gas inventory to deliver the UK’s Assigned Amount under the
Kyoto Protocol.
Table ES1 shows the overall change in carbon emissions using the updated
carbon factors for solid, liquid and gaseous fuels.
Table ES1: Overall change in carbon emissions (MtC)
Year
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
% change
1990-2002
2002 GHG inventory
164.63
165.66
161.62
157.45
156.27
153.83
159.35
152.65
153.46
151.13
152.17
155.75
150.26
-8.73%
Review of Carbon Emission Factors
Emissions using
updated factors
165.88
167.43
163.02
158.62
157.31
154.17
160.31
153.84
155.03
152.07
152.92
157.09
151.79
Difference
1.26
1.77
1.40
1.17
1.05
0.34
0.96
1.19
1.57
0.93
0.76
1.33
1.52
% difference
0.76
1.07
0.86
0.75
0.67
0.22
0.60
0.78
1.02
0.62
0.50
0.86
1.02
-8.49%
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List of Contents
Table of Contents
1
2
Introduction
1
1.1
1.2
1.3
1.4
1
2
2
3
Overview of the changes in estimated GHG emissions
due to the revisions in the selected CEFs
2.1
2.2
2.3
3
BACKGROUND TO THIS PROJECT
GENERAL APPROACH TO THE CEF REVIEW
FUELS REVIEWED
QUOTED ACCURACY OF THE EMISSIONS IN THIS STUDY
ORIGINAL AND REVISED CARBON EMISSION FACTORS
CONTRIBUTIONS OF FUELS TO CARBON EMISSIONS IN
INVENTORY
UNITS OF CEFS USED IN THE UK GHG INVENTORY
4
6
6
Solid fuels
8
3.1
3.2
INTRODUCTION
CEFS OF SOLID FUELS USED IN THE 2002 GHG INVENTORY
3.2.1
Coal
3.2.2
Coke
3.2.3
Anthracite
3.2.4
Petroleum coke
3.3 REVISED CEFS
3.3.1
Fraction of fuel unoxidised after combustion
3.3.2
Coal – ESI sector
3.3.3
Coal – Other sectors
3.3.3.1
3.3.3.2
3.3.4
3.3.5
3.3.5
4
Other sectors – excluding cement production
Cement production
17
17
17
Non-cement industry consumers
Cement industry
17
18
EFFECT OF REVISING THE CEFS FOR SOLID FUELS ON
CARON EMISSIONS
3.4.1
Coal – ESI sector
3.4.2
Coal, anthracite, coke - other sectors
3.4.3
Petroleum coke
3.4.4
Overall change to carbon emissions resulting from
revisions to the CEFs of the solid fuels
18
18
20
22
22
Gaseous fuels
4.1
4.2
23
INTRODUCTION
CEFS OF GASEOUS FUELS USED IN THE 2002 GHG
INVENTORY
4.2.1
Natural Gas
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8
8
8
9
10
10
10
10
10
12
12
17
Coke
Anthracite
Petroleum coke
3.3.5.1
3.3.5.2
3.4
4
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23
23
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List of Contents
4.2.2
Coke oven gas
4.2.3
Blast furnace gas
4.2.4
Other petroleum gas (OPG)
4.3 REVISED CEFS
4.3.1
Fraction of fuel unoxidised after combustion
4.3.2
Natural gas
4.3.3
Coke oven gas
4.3.4
Blast furnace gas
4.3.5
Other petroleum gas
4.4 EFFECT OF REVISING THE CEFS FOR GASEOUS FUELS ON
CARBON EMISSIONS
4.4.1
Natural gas
4.4.1.1
4.4.2
4.4.3
4.4.4
4.4.5
5
Database
26
26
27
Blast furnace gas
Coke oven gas
Other petroleum gas (OPG)
Overall change to carbon emissions resulting from
revisions to the CEFs of the gaseous fuels
28
28
29
29
Liquid fuels
30
5.1
5.2
5.3
INTRODUCTION
CEFS OF LIQUID FUELS USED IN THE 2002 GHG INVENTORY
REVISED CEFS
5.3.1
Fraction of fuel unoxidised after combustion
5.4 EFFECT OF REVISING THE CEFS FOR LIQUID FUELS ON
CARBON EMISSIONS
5.4.1
Naphtha
5.4.2
Aviation spirit
5.4.3
Fuel Oil
5.4.4
Gas oil
5.4.5
Diesel oil
5.4.6
Overall change to carbon emissions resulting from
revisions to the CEFs of the liquid fuels
6
24
24
24
24
24
24
26
26
26
30
31
31
33
33
33
34
34
35
35
35
Overall effect on carbon emissions of the revised
CEFs
37
7
References
41
8
Acknowledgements
43
Appendix 1
44
A1.1 BUNKER EMISSIONS
A1.2 GROSS CALORIFIC VALUES
A1.3 CONVERSION FACTORS FOR GROSS TO NET ENERGY
CONSUMPTION
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46
49
Page
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List of Contents
Appendix 2
50
A2.1 REVIEW OF FRACTIONS OF CARBON LEFT UNOXIDISED
AFTER COMBUSTION IN LIQUID FUELS
50
Appendix 3
52
A3.1 PROJECT MEETINGS
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List of Contents
Document revision history
Issue
Version
Revision history
1.3
1.3.1
1.3.2
•
•
•
•
•
Draft
1.0
1.0
1.0
Issued to UK Defra for internal review and comment
Comments incorporated
First issue
Minor typographical errors corrected
Minor typographical errors corrected in the headers and
footers
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List of Contents
Abbreviations, acronyms and definitions
Greenhouse gases
CH4
Methane
CO2
Carbon dioxide
N2O
Nitrous oxide
General
AEP
Association of Electricity Providers
www.aepuk.com
AS
ATF
BCA
BFG
C
CEF
COG
CORUS
DTI
DERV
Aviation Spirit
Aviation Turbine Fuel
British Cement Association
Blast Furnace Gas
Carbon
Carbon Emission Factor
Coke Oven Gas
The owner of the many of the integrated steel works in the
UK
UK Department of Trade and Industry
Diesel Engined Road Vehicle
fuel used in internal combustion engines that are compression ignition
engines
DUKES
Digest of United Kingdom Energy Statistics
www.dti.gov.uk/energy/statistics
EA
Environment Agency
for England and Wales
EU
ESI
ETS
GCV
GHG
GHGI
IPCC
JEP
European Union
Electricity Supply Sector
Emissions Trading Scheme
Gross Calorific Value
Greenhouse gas
Greenhouse gas inventory
Intergovernmental Panel on Climate Change
Joint Environmental Programme
funded by the Association of Electricity Producers (AEP)
kt
LPG
kilotonne
Liquid Petroleum Gas
composed of a variable mixture of propane and butane
Mt
NG
Mega tonne
Natural gas
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List of Contents
OPG
SSF
SEPA
TRANSCO
Other Petroleum Gas
Solid Smokeless Fuel
Scottish Environmental Protection Agency
Gas transportation company
Ceased to exists in 2005, and now part of National Grid UK
UK
UKPIA
United Kingdom
UK Petroleum Industry Association
Trade association which represents the oil refining and marketing
industry in the United Kingdom
www.ukpia.com
UN/ECE
UNFCCC
United Nations Economic Commission for Europe
United Nations Framework Convention on Climate Change
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Introduction 1
1
Introduction
1.1
BACKGROUND TO THIS PROJECT
The United Nations Framework Convention on Climate Change (UNFCCC)
was ratified by the United Kingdom in December 1993 and came into force in
March 1994. Parties to the Convention are committed to develop, publish and
regularly update national emission inventories of greenhouse gases (GHGs).
The UK has been compiling and submitting GHG inventories to the FCCC
since 1994.
AEA Energy & Environment, on behalf of UK Defra, has prepared the latest
(at the time this report was written) greenhouse gas inventory (GHGI) and
associated tables of emissions in CRF format according to UNFCCC
guidelines contained in FCCC/CP/2002/8 (Baggott et. al., 2004). The
estimates within the inventory have been generated by following the methods
and procedures set out in the IPCC Revised 1996 Guidelines for National
Greenhouse Gas Inventories (IPCC, 1997a, b, c) and Good Practice
Guidance and Uncertainty Management in National Greenhouse Gas
Inventories (IPCC, 2000).
The UK GHGI is subject to a range of external reviews. At the time this report
was written, these reviews include reviews by experts from the FCCC during
desk, centralised and in-country reviews, and, by invited independent
examiners during a process of peer review. The Intergovernmental Panel on
Climate Change (IPCC) Good Practice Guidance (IPCC, 2000) defines expert
peer review as follows:
‘Expert peer review consists of a review of calculations or assumptions by
experts in relevant technical fields. This procedure is generally
accomplished by reviewing the documentation associated with the
methods and results, but usually does not include rigorous certification of
data or references such as might be undertaken in an audit. The
objective of the expert peer review is to ensure that the inventory's
results, assumptions, and methods are reasonable as judged by those
knowledgeable in the specific field.’
The Good Practice Guidance requires that key sources should be subjected
to external peer review. Key sources are those source categories with a
significant influence on a country’s total inventory of direct greenhouse gases
in terms of the absolute level of emissions, the trend in emissions, or both.
The first peer review of the GHGI considered CO2 emissions from fuel
combustion (Simmons, 2002). This topic was chosen for peer review since
IPCC sector 1A11 was identified as a key source because of the magnitude of
emissions of carbon dioxide (CO2) from the combustion of solid, liquid and
1
Emissions from fuels combusted by the fuel extraction or energy producing industries.
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Introduction 1
gaseous fuels in that sector. In addition, fossil fuel combustion is the major
source of UK emissions of carbon dioxide.
A key recommendation of this peer review was that the carbon emission
factors (CEFs) currently used in the inventory should be reviewed:
‘Many of the carbon emission factors used in the inventory date from
1989. Whilst they may still be accurate for the fuels used today there
have been changes to the sources of fuels over the period of the
inventory and changes in their qualities to reflect environmental
requirements. It is recommended that the carbon content factors be
reviewed, together with related factors accounting for incomplete
oxidation of the fuels during combustion.’
This report presents the results of a review of the CEFs used in the 2004 UK
National Inventory Report, containing the 2002 GHG inventory (1990 to 2002
inclusive). This work is important to the overall quality of the GHG estimates
since accurate estimates of the carbon contents of fuels determine the
accuracy of the estimated CO2 emissions.
1.2
GENERAL APPROACH TO THE CEF REVIEW
A programme of work was developed to review CEFs of the fuels in the UK
greenhouse gas inventory. The review concentrated on a selection of key
fuels that contribute to the greatest proportions of CO2 emissions. A range of
stakeholders were consulted during the review process, including industry
experts within the UK electricity supply industry, the petroleum industry, and
the gas supply industry. To support this work, a selection of liquid fuels were
analysed, on behalf of UKPIA, to determine their carbon contents. Analysis of
gas composition data from TRANSCO was also considered. In addition, data
presented in a range of reports (including data on UK CEFs, calorific values,
fractions of fuels left unoxidised after combustion, and fuel compositions)
were reviewed. A range of parties examined the initial recommendations for
revised CEFs including industry experts and government representatives of
the UK Energy Trading Scheme (UK ETS). Their recommendations were
considered before the final set of CEFs was selected for the GHGI.
Following this review, CEFs were introduced into the 2002 greenhouse gas
inventory, and the changes in the carbon emissions were quantified.
1.3
FUELS REVIEWED
An analysis of the quantities of fuel consumed according to IPCC sector was
completed in order to identify which fuels contributed the most to emissions of
CO2 in the UK. This analysis clearly showed that the main effort of the work
should be concentrated on revising the CEFs for natural gas, coal and the
liquid fuels. The CEFs of other fuels were reviewed during the course of this
work; the reason for selecting these additional fuels was to satisfy demands
for revised CEFs for the UK ETS.
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Introduction 1
1.4
QUOTED ACCURACY OF THE EMISSIONS IN THIS
STUDY
In this report, emissions are quoted to 0.01 ktonne (or better) purely for
convenience, to avoid the risk of rounding errors, and for convenience when
taking ratios. The number of decimal places used should not be taken as
indicative of the accuracy of the estimates.
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Overview 2
2
Overview of the changes in estimated
GHG emissions due to the revisions in
the selected CEFs
This chapter of the report presents a summary of the changes in estimated
GHG emissions due to the revisions in the selected CEFs. Table 2.1 shows
the values of the original CEFs used in the 2002 GHGI for 1990 and 2002,
and the revisions to those CEFs. The changes in emissions are summarised
according to fuel, and IPCC reporting sector. Table 2.1 shows the overall
effect on the revised CEFs on the national GHG totals.
2.1
ORIGINAL AND REVISED CARBON EMISSION
FACTORS
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Overview 2
Table 2.1:
Fuel Type
Solid
Original and revised CEFs values used in the 2002 GHGI for 1990 and 2002 (KtC/Mt fuel for solid and liquid fuels,
and Kt/Mtherm for gaseous fuels)
Consumer
IPCC Fuel
Original CEF 1990
Revised CEF 1990 Original CEF 2002
Revised CEF 2002
Petcoke
800
930
800
930
Petcoke (cement)
800
829.6
800
829.6
Agriculture
Other bituminous coal
659.6
656.6
659.6
650.4
Autogenerators
Other bituminous coal
659.6
659.6
659.6
628.7
Cement (combustion)
Other bituminous coal
659.6
757.7
659.6
725.5
Collieries
Other bituminous coal
659.6
659.6
659.6
684.9
Domestic
Other bituminous coal
676.8
676.8
676.8
696.9
Domestic
Anthracite
813.4
813.4
813.4
820.6
ESI
Other bituminous coal
588.2
605
588.2
627.2
Iron & Steel blast furnaces
Coking coal
710
694
Iron & Steel (combustion)
Other bituminous coal
659.6
659.6
659.6
693.8
Lime production (combustion) Other bituminous coal
659.6
659.6
659.6
628.7
Miscellaneous
Other bituminous coal
659.6
659.6
659.6
721.9
Other industry
Other bituminous coal
659.6
659.6
659.6
633.5
Public services
Other bituminous coal
659.6
659.6
659.6
721.9
Railways (stationary sources) Other bituminous coal
659.6
659.6
659.6
721.9
Liquid
Aviation spirit
850
853
865
853
Diesel Oil
857
864
857
863
Fuel Oil
850
867
850
879
Gas Oil
857
869
857
870
Naphtha
940
854
940
854
Residual Fuel Oil
850
867
850
879
Gaseous
Natural Gas
1.50
1.45
1.50
1.48
Blast Furnace Gs
6.27
7.46
6.27
7.46
Other Petroleum Gas
1.68
1.64
1.63
1.64
• The original CEFs are taken from the 2002 GHGI
• ESI – Electricity Supply Industry
• Emissions of the gaseous fuels are gross
• The CEFs for solid fuels in this table account for the incomplete oxidation of the fuels following combustion. Oxidation factors are considered in
Chapters 3, 4 and 5.
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Overview 2
2.2
CONTRIBUTIONS OF FUELS TO CARBON EMISSIONS IN
INVENTORY
Different fuels contribute different amounts to overall carbon emissions in the UK.
It is those fuels that contribute the most to emissions that will have the most
significant effect on emissions if their factors are altered. Table 2.2 list the major
contributors to carbon emissions both in 1990 and 2002.
Table 2.2:
Percentage contributions of fuels to overall carbon emissions in the
UK in 1990 and 2002
Fuel
Coal
Natural Gas
Petrol
Fuel oil
DERV
Gas Oil
Blast Furnace Gas
OPG
Coke
Clinker Production
Burning Oil
Aviation Turbine Fuel
Anthracite
SSF
Coke Oven Gas
LPG
Limestone
Petroleum Coke
1990
35
19
13
7
6
4
3
1
1
1
1
1
1
1
1
1
1
-
2002
21
38
11
2
10
4
2
1
1
1
2
1
1
1
The fuels listed in the above table contribute 97% to overall carbon emissions in
1990 and 2002. In each year, the remaining 3% is made up of a number of other
fuels, each contributing 1% or less to the overall total.
In both 1990 and 2002 the top three contributors remain the same – natural gas,
coal and petrol, although the relative contribution from coal decreases and the
importance of natural gas increases in 2002, relative to 1990.
2.3
UNITS OF CEFs USED IN THE UK GHG INVENTORY
The emission factors used in the 2002 UK GHG inventory are expressed in terms
of kg pollutant/tonne for solid and liquid fuels, and g/TJ gross for gases. This
differs from the IPCC approach which expresses emission factors as tonnes
pollutant/TJ based on the net calorific value of the fuel. For gases the factors used
in the UK GHG inventory are based on the gross calorific value of the fuel. This
approach is used because the gas consumption data in commodity balance tables
produced by the UK DTI are reported in terms of energy content on a gross basis.
Emissions factors for solid and liquid fuels are in terms of mass. These mass
based factors can then be applied to consumptions of UK fuels expressed on a
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Overview 2
mass basis published by the DTI. Emissions factors for natural gas are in terms of
the energy content of the gas consumed (g carbon/GJ gross). These energy
based factors can then be applied to consumptions of UK fuels expressed on a
energy basis published by the DTI.
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Solid fuels 3
3
Solid fuels
3.1
INTRODUCTION
Within the UK, the main solid fuels that are used are coal, anthracite, coke and
petroleum coke. In 1990 coal was the major contributor to carbon greenhouse gas
emissions, with 34% of emissions arising from this fuel. This declined to 21% in
2002. The main user of coal is the power station sector, which accounted for
88.5% of emissions in 2002. Table 3.1 displays the main sectors that use coal in
the UK and their percentage contribution to overall carbon emissions
Table 3.1
Significant sources of coal in the UK
Source
Power Stations
Coke Production
Public Services
Domestic
Autogenerators
Other Industry combustion
Cement fuel combustion
Lime production - combustion
% contribution to
overall coal emission
88.5
1.2
0.3
2.2
3.4
3.2
0.8
0.2
Minor emissions also occur from the Iron and steel industry, agriculture, railways,
collieries and miscellaneous sources.
Coke use in the UK accounted for 1% of overall carbon emissions in the UK in
2002. Coke is mainly used by the iron and steel industry and in 2002, emissions
from this sector accounted for 69% of emissions. Other significant emissions arise
from combustion in other industry and domestic use.
Petroleum coke emissions accounted for 1% of overall carbon emissions in the UK
in 2002. Petroleum coke is used mainly by the refineries sector (48% of emissions
in 2002) and the cement industry (40% of emissions in 2002).
3.2
CEFs OF SOLID FUELS USED IN THE 2002 GHG
INVENTORY
3.2.1
Coal
The current carbon emission factors for coal were supplied to AEA Technology by
British Coal in 1989. Since then, the emission factors used have not been altered.
The production of coal within the UK declined steadily during the 1990s and
gradually more coal has been imported from elsewhere. Due to this change in the
mix of home/imported coal now used in the UK, the factors were reviewed.
All the coal CEFs in the inventory take into account the proportion of un-oxidised
carbon that remains in the ash after combustion. Table 3.2 shows the assumed
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Solid fuels 3
oxidation factors for each type of coal and the corresponding un-oxidised carbon
emission factor.
Table 3.2:
Carbon retention in ash figures for coal use in UK in the 2004 GHG
inventory
Coal use
Power Stations
Other
Domestic
Un-oxidised
factor (kt/Mt)
590
680
720
C retention in
ash (%)
0.3
3
6
Oxidation
factor
0.997
0.97
0.940
Oxidised factor
(kt/Mt)
588.2
659.6
676.8
Table 3.3 displays the sources of coal emissions in the inventory and their
corresponding emission factors.
Table 3.3:
Current coal emission factors (kt/Mt)
Source
Power Stations
Public Services
Domestic
Autogenerators
Other Industry combustion
Cement fuel combustion
Lime production - combustion
Current coal emission
factor (kt/Mt)
588.2
659.6
676.9
659.6
659.6
659.6
659.6
Minor emissions also occur from the iron and steel industry, agriculture, railways,
collieries and other miscellaneous sources. The emission factor used for iron and
steel blast furnaces is currently 710 kt/Mt and for other sources mentioned, the
emission factor used is 659.6 kt/Mt.
3.2.2
Coke
Coke emissions in the inventory arise from a variety of sources and overall
contribute 1% to carbon emissions in the UK. Currently, as with coal, the factors
were supplied by British Coal in 1989.
As with coal, assumptions were made about the proportion of un-oxidised carbon
left after combustion. Table 3.4 shows the assumed oxidation factors for coke and
the corresponding un-oxidised carbon emission factor along with the oxidised
factor that is currently used in the UK GHGI.
Table 3.4:
Coke use
Domestic
Power stations
Other
Carbon retention in ash figures for coke use in UK
Un-oxidised
factor (kt/Mt)
820
820
820
C retention in
ash (%)
2
3
3
Oxidation
factor
0.98
0.97
0.97
Oxidised factor
(kt/Mt)
803.6
795.4
795.4
Table 3.5 displays the sources of coke emissions in the inventory and their
corresponding emission factors.
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Solid fuels 3
Table 3.5:
Sources of coke emissions and corresponding emission factors
Source
Domestic
SSF production
Coke production
Iron and Steel (sinter)
Other industry (combustion)
Iron and steel (combustion)
Lime production (combustion)
Power stations
Railway (stationary sources)
Public services
Agriculture
Miscellaneous
Current coke emission
factor (kt/Mt)
803.6
820
795.4
Emissions from iron and steel blast furnaces are calculated from a mass balance
approach (see Section 3.4.2).
3.2.3
Anthracite
Carbon emissions from anthracite occur from the domestic sector only. The
current carbon content of anthracite was supplied by British Coal in 1989 and has
a value of 859 kt/Mt. This has a correction applied to it for the un-burnt fraction of
carbon of 5.3%, giving the carbon emission factor of 813.4 kt/Mt.
3.2.4
Petroleum coke
The current factor for petroleum coke was supplied by the UK Petroleum Institute
Association (UKPIA) in 1989. The value is 800 ktC/Mt and applies to all sectors
burning petroleum coke.
3.3
REVISED CEFs
3.3.1
Fraction of fuel unoxidised after combustion
The CEFs in this section account for the carbon left unoxidised after combustion.
3.3.2
Coal – ESI sector
Power stations are the major contributor to carbon emissions from coal
combustion, and so obtaining updated emission factors for this sector was
considered a priority.
A time series (1990-2003) of updated carbon emission factors (Table 4.6) was
obtained from Powertech (Quick, 2004). It was advised that data in this time series
was based on Powergen operated sites only but would be fairly representative of
the UK as a whole. These updated emission factors took into account the increase
in the UK’s use of imported coals as well as a carbon in ash content (i.e. un-burnt
carbon).
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Solid fuels 3
Table 3.6:
Carbon emission factors provided by Quick (2004)
Year
% C in coal
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
60.37
61.05
60.78
60.78
60.63
59.73
60.92
61.74
62.35
61.94
61.76
62.54
62.99
62.58
% C in Coal corrected for 5% C in ash,
13% ash coal
59.69
60.37
60.10
60.10
59.95
59.05
60.24
61.06
61.67
61.26
61.08
61.86
62.31
61.90
Kte C/Mte coal burnt
596.86
603.66
600.96
600.96
599.46
590.46
602.36
610.56
616.66
612.56
610.76
618.56
623.06
618.96
A working paper from the Association of Electricity Producers (AEP) (Joslin et al,
2004) detailing their recommended carbon content of fuel and oxidation factor for
2003 was also obtained. This paper recommended a carbon content of 0.64 and
an oxidation factor of 0.98. After discussion with both the AEP and Powergen it
was established that the slightly higher carbon content quoted by the AEP was due
to the influence of Aberthaw power station which burns coal with a higher carbon
content. There was also a difference in the oxidation factor between the
Powertech and AEP studies, and this occurs for two primary reasons. Firstly, the
influence of Aberthaw, which due to its unique nature has high carbon content in
ash. Secondly, Powergen stations have tended to be run as ‘base-load’ stations
more than others, which invariably results in better combustion performance and
lower carbon in ash (Quick, 2004b). It was therefore agreed by all parties that the
time series of emission factors provided by Quick (2004) should be scaled to the
AEP carbon content for 2003. It was also agreed that the oxidation factor of 0.98
should be used.
Both these assumptions were considered to provide
representative parameters from coal use within the UK.
Taking these changes into account, proposed new carbon emission factors for the
Greenhouse Gas Inventory are shown in Table 3.7. Emission factors are scaled
as follows:
A * (0.64/0.6258) = Carbon Emission Factor
Where A = Carbon emission factor provided by Quick
So in 2003, Carbon emission factor = 0.6258 * (0.64/0.6258) = 0.64
Applying the oxidation factor of 0.98 provides a carbon emission factor of 0.6272.
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Solid fuels 3
Table 3.7:
Year
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
3.3.3
AEP scaled Carbon emission factors
% C in coal
61.74
62.44
62.16
62.16
62.01
61.09
62.30
63.14
63.76
63.35
63.16
63.96
64.42
64.00
% C in coal corrected for 2% C in ash
60.51
61.19
60.92
60.92
60.77
59.86
61.06
61.88
62.49
62.08
61.90
62.68
63.13
62.72
kte/Mte coal burnt
605.05
611.87
609.16
609.16
607.66
598.64
610.56
618.78
624.89
620.79
618.80
626.80
631.31
627.20
Coal – Other sectors
3.3.3.1
Other sectors – excluding cement production
Table 3.1 shows that the ESI sector is an important contributor to carbon
emissions from coal combustion in the UK. Other sectors that use coal contribute
just over 10% to overall emissions, with most of these sectors individually
contributing less than 1% to totals. A full review and consultation with all the
industry representatives in these sectors was not considered to be a wise use of
resources in this project, and so an approach was developed to scale existing
CEFs to GCVs reported in DTI (2003) relative to 1990. Carbon emission factors
and GCVs are closely related and so an increase or decrease in a GCV is likely to
reflect similarly in the carbon content of the fuel. Tables 3.8 to 3.11 display the
results of the simple method used to calculate revised emission factors for the
sectors consuming smaller quantities of coal. The cement sector is considered
later.
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Solid fuels 3
Table 3.8:
Carbon emission factors used in the 2002 GHG inventory
Source
Agriculture
Coke Production
Collieries
Domestic
I&S (blast furnace)
I&S (combustion)
Lime Production
(combustion)
Miscellaneous
Other Industry
(combustion)
Public services
Railways (stationary
sources)
SSF production
Autogenerators
Cement (Fuel
combustion)
1990
659.6
41.87
659.6
676.8
1991
659.6
38.29
659.6
676.8
1992
659.6
31.42
659.6
676.8
1993
659.6
34.08
659.6
676.8
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
127.22
659.6
659.6
Review of Carbon Emission Factors
659.6
659.6
1994
659.6
34.31
659.6
676.8
710
659.6
659.6
1995
659.6
40.61
659.6
676.8
710
659.6
659.6
1996
659.6
36.74
659.6
676.8
710
659.6
659.6
1997
659.6
45.21
659.6
676.8
710
659.6
659.6
1998
659.6
44.84
659.6
676.8
710
659.6
659.6
1999
659.6
58.09
659.6
676.8
710
659.6
659.6
2000
659.6
42.85
659.6
676.8
710
659.6
659.6
2001
659.6
58.57
659.6
676.8
710
659.6
659.6
2002
659.6
58.54
659.6
676.8
710
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
659.6
79.47
659.6
659.6
77.52
659.6
659.6
49.59
659.6
659.6
23.56
659.6
659.6
33.43
659.6
659.6
93.15
659.6
659.6
135.47
659.6
659.6
46.64
659.6
659.6
36.45
659.6
659.6
27.39
659.6
659.6
37.33
659.6
659.6
33.87
659.6
659.6
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Solid fuels 3
Table 3.9:
GCVs reported in the DTI DUKES publication
Source
Agriculture
Collieries
Domestic
I&S (blast
furnace)
I&S (combustion)
Lime Production
(combustion)
Miscellaneous
Other Industry
(combustion)
Public services
Railways
(stationary
sources)
Autogenerators
Cement (Fuel
combustion)
DUKES class
Agriculture
Collieries
House Coal
Coke Ovens: Home
& Imports
Iron and steel
industry
Other industries
1990
28.9
28.6
30.2
31.2
1991
28.9
28
30.2
31.4
1992
28.9
26.8
30.2
31.45
1993
28.7
26.8
30.2
31.46
1994
28.8
28.2
29.8
31.43
1995
29
28.2
30.4
31.4
1996
28.9
26.2
30.6
32
1997
29.1
27.8
30.6
32
1998
28.5
29.6
30.9
32
1999
28.9
29.3
30.9
30.5
2000
29.2
29.6
30.9
30.4
2001
29.8
29.8
30.9
30.5
2002
28.5
29.7
31.1
30.5
28.9
28.9
28.9
28.7
29.4
31.5
31.3
31.3
31.3
30.7
30.7
29.4
30.4
27.8
27.8
27.8
28.1
28.8
27.7
27.3
27
26.9
26.6
26.8
26.7
26.5
Other Consumers
Other Industries
27.5
27.8
27.5
27.8
27.5
27.8
28.7
28.1
28.8
28.8
28.9
27.7
30.4
27.3
29.3
27
29.2
26.9
29.1
26.6
29.2
26.8
29.2
26.7
30.1
26.5
Other Consumers
Other Consumers
27.5
27.5
27.5
27.5
27.5
27.5
28.7
28.7
28.8
28.8
28.9
28.9
30.4
30.4
29.3
29.3
29.2
29.2
29.1
29.1
29.2
29.2
29.2
29.2
30.1
30.1
Other Industries
Other Industries
27.8
27.8
27.8
27.8
27.8
27.8
28.1
28.1
28.8
28.8
27.7
27.7
27.3
27.3
27
27
26.9
26.9
26.6
26.6
26.8
26.8
26.7
26.7
26.5
26.5
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Solid fuels 3
Table 3.10: Ratios of GCVs relative to 1990
Source
Agriculture
Collieries
Domestic
I&S (blast furnace)
I&S (combustion)
Lime Production (combustion)
Miscellaneous
Other Industry (combustion)
Public services
Railways (stationary sources)
Autogenerators
Review of Carbon Emission Factors
1990
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1991
1.00
0.98
1.00
1.01
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1992
1.00
0.94
1.00
1.01
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1993
0.99
0.94
1.00
1.01
0.99
1.01
1.04
1.01
1.04
1.04
1.01
1994
1.00
0.99
0.99
1.01
1.02
1.04
1.05
1.04
1.05
1.05
1.04
1995
1.00
0.99
1.01
1.01
1.09
1.00
1.05
1.00
1.05
1.05
1.00
AEA Energy & Environment
1996
1.00
0.92
1.01
1.03
1.08
0.98
1.11
0.98
1.11
1.11
0.98
1997
1.01
0.97
1.01
1.03
1.08
0.97
1.07
0.97
1.07
1.07
0.97
1998
0.99
1.04
1.02
1.03
1.08
0.97
1.06
0.97
1.06
1.06
0.97
1999
1.00
1.02
1.02
0.98
1.06
0.96
1.06
0.96
1.06
1.06
0.96
2000
1.01
1.04
1.02
0.97
1.06
0.96
1.06
0.96
1.06
1.06
0.96
2001
1.03
1.04
1.02
0.98
1.02
0.96
1.06
0.96
1.06
1.06
0.96
2002
0.99
1.04
1.03
0.98
1.05
0.95
1.09
0.96
1.09
1.09
0.95
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Solid fuels 3
Table 3.11: Revised carbon emission factors for coal
Source
Agriculture
Collieries
Domestic
I&S (blast furnace)
I&S (combustion)
Lime Production
(combustion)
Miscellaneous
Other Industry
(combustion)
Public services
Railways
(stationary
sources)
Autogenerators
1990
659.60
659.60
676.80
659.60
659.60
1991
659.60
645.76
676.80
659.60
659.60
1992
659.60
618.09
676.80
659.60
659.60
1993
655.04
618.09
676.80
655.04
666.72
1994
657.32
650.37
667.84
715.23
671.01
683.33
1995
661.88
650.37
681.28
714.55
718.94
657.23
1996
659.60
604.25
685.76
728.21
714.38
647.74
1997
664.16
641.15
685.76
728.21
714.38
640.62
1998
650.47
682.66
692.49
728.21
714.38
638.25
1999
659.60
675.74
692.49
694.07
700.38
631.13
2000
666.45
682.66
692.49
691.79
700.38
635.87
2001
680.14
687.28
692.49
694.07
671.01
633.50
2002
650.47
684.97
696.97
694.07
693.84
628.76
659.60
659.60
659.60
659.60
659.60
659.60
688.38
666.72
690.78
683.33
693.18
657.23
729.16
647.74
702.77
640.62
700.38
638.25
697.98
631.13
700.38
635.87
700.38
633.50
721.96
633.50
659.60
659.60
659.60
659.60
659.60
659.60
688.38
688.38
690.78
690.78
693.18
693.18
729.16
729.16
702.77
702.77
700.38
700.38
697.98
697.98
700.38
700.38
700.38
700.38
721.96
721.96
659.60
659.60
659.60
666.72
683.33
657.23
647.74
640.62
638.25
631.13
635.87
633.50
628.76
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Solid fuels 3
3.3.3.2
Cement production
We contacted the trade association for the UK cement producers - the British Cement
Association (BCA) – and the National Energy Manager for Lafarge cement to gather
information about the current usage and combustion conditions of coal in the cement
sector. Cement kilns operate at high temperatures (for example, temperatures in the
sintering zone of rotary kilns are around 1,450°C) and so fuels will be almost completely
oxidised, and effectively 100% oxidation is achieved. The BCA indicated that the UK
cement industry tends to now source their coal from abroad, whereas the current GHG
inventory assumed UK coal is consumed. Therefore, the approach of directly scaling
the current carbon factors to GCVs was felt to be unsuitable for this industry.
The time series of carbon emission factors (see Table 3.12) for coal used in the cement
sector was provided by Rushworth (2004) and was based on the empirical relationship
between calorific values and carbon emissions established using actual data for the
years 2000 to 2004. Calorific values for mineral products for the years 1990 to 1999
were taken from DUKES (DTI, 2004) Table A2. These calorific values are supplied to
the DTI by the BCA and therefore are consistent with the empirical relationship derived.
Table 3.12: Carbon emission factors and GCV for coal used by the UK cement
industry
Emission
factor
kt/Mt
GCV GJ
per
tonne
3.3.4
1990
757.8
1991
757.8
1992
757.8
1993
792.7
1994
760.4
1995
728.2
1996
736.3
1997
725.5
1998
714.8
1999
717.5
2000
725.5
2001
725.5
2002
725.5
2003
749.7
2004
744.3
28.2
28.2
28.2
29.5
28.3
27.1
27.4
27.0
26.6
26.7
27.0
27.0
27.0
27.9
27.7
Coke
Calorific values for coke remained constant throughout the time series and so the
factors remained unaltered.
3.3.5
Anthracite
In the UK inventory, carbon emissions from anthracite occur from domestic sources
only. Anthracite emission factors were scaled to GCVs as described for coal.
Table 4.13 presents the carbon emission factors found in the current inventory,
corresponding GCVs, and revised of emission factors.
Table 3.13: Current and proposed emission factors for anthracite (kt/Mt)
Current EF
1990
813.4
1991
813.4
1992
813.4
1993
813.4
1994
813.4
1995
813.4
1996
813.4
1997
813.4
1998
813.4
1999
813.4
2000
813.4
2001
813.4
2002
813.4
GCV (GJ/t)
33.6
33.6
33.5
33.5
33.6
34.0
33.9
33.9
34.1
33.5
33.6
33.9
33.9
Proposed
EF
813.4
813.4
811.0
811.0
813.4
823.1
820.7
820.7
825.5
811.0
813.4
820.7
820.7
3.3.5
Petroleum coke
3.3.5.1
Non-cement industry consumers
The UK Petroleum Industry Association (UKPIA) provided an updated estimate for the
carbon factor for UK petroleum coke (UKPIA, 2004). The estimate was based on
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Solid fuels 3
analytical results of the carbon contents of UK petroleum coke. UKPIA recommended
that the new factor should be 930 ktC/Mt across the whole time series, but this factor
was not used for petroleum coke used by the cement sector.
3.3.5.2
Cement industry
The cement industry use petroleum coke, and we consulted the BCA about the sources
and carbon contents of the fuel consumed. The BCA reported that all the petroleum
coke consumed is not sourced from UK refineries, but is imported, and so the carbon
emission factor supplied by UKPIA would not be applicable to the petroleum coke used
by the UK cement industry. The BCA provided measured carbon contents for
petroleum coke for 2000 to 2004. These data were averaged, and applied across the
time series, from 1990 to 2004. The industry normally tightly controls the energy
content of its fuels and the industry’s European database shows emission factors
across samples to be very similar. Therefore, applying a constant CEF to the time
series seems a reasonable assumption.
The BCA recommended a carbon emission factor of 829.6 ktC/Mt for the cement sector
and this has been adopted.
3.4
EFFECT OF REVISING THE CEFs FOR SOLID FUELS ON
CARON EMISSIONS
3.4.1
Coal – ESI sector
Tables 3.14 to 3.16 present the effects of introducing the revised coal CEFs for the ESI
into the 2002 GHG inventory. Table 3.14 displays the difference between overall UK
carbon emissions from coal combustion before and after the CEF update for the ESI
sector. Table 3.15 shows the difference in the ESI sector only and finally Table 3.16
displays the overall differences observed in carbon emissions (from the combustion of
all fuels) in the UK.
Table 3.14: Changes in carbon emissions from coal (total for all sources consuming
coal) after applying the revised coal CEF to the ESI (Mt)
Year
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
Emissions in the
original 2002 GHG
inventory
57.25
56.95
53.60
43.31
42.20
39.71
36.49
31.72
31.97
27.90
29.34
33.09
30.68
Emissions using revised
CEFs
% change to coal
emissions
58.64
58.89
55.21
46.65
43.38
40.31
37.68
31.11
33.68
29.19
30.72
34.99
32.66
2.43
3.41
3.01
2.96
2.79
1.52
3.27
4.36
5.35
4.62
4.69
5.75
6.48
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Solid fuels 3
Table 3.15: Changes in carbon emissions from the ESI sector after applying the
revised coal CEF to the ESI (Mt)
Year
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
Emissions in the
original 2002 GHG
inventory
48.56
48.25
45.29
37.70
35.68
34.08
31.43
26.66
27.43
23.28
26.33
28.99
27.14
Emissions using revised
CEFs
% change to ESI coal
emissions
49.95
50.19
46.90
39.04
36.85
34.69
32.62
28.04
29.14
24.57
27.71
30.90
29.13
2.86
4.02
3.56
3.56
3.30
1.77
3.80
5.19
6.23
5.54
5.23
6.56
7.32
Table 3.16: Changes to overall UK carbon emissions after applying the revised coal
CEF to the ESI (Mt)
Year
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
Emissions in the
original 2002 GHG
inventory
164.63
165.66
161.62
157.45
156.26
153.83
159.35
152.65
153.46
151.13
152.17
155.75
150.26
Emissions using revised
CEFs
% change to emissions
166.02
167.60
163.23
158.79
157.44
154.43
160.54
154.03
155.17
152.42
153.54
157.65
152.25
0.84
1.17
1.00
0.85
0.75
0.39
0.75
0.91
1.11
0.85
0.90
1.22
1.32
Table 3.17 displays the overall percentage changes in carbon emissions between 1990
and 2002. It shows the decline in overall carbon emissions from the 2002 GHG
inventory (from 1990 to 2002), and the decline in the carbon emissions after the revised
CEF has been applied in the ESI sector. The effect of introducing the new CEF into the
ESI sector is to reduce the decline in carbon emissions, although the effect is small.
Table 3.17: Percentage change in overall carbon emissions between 1990 and 2002
GHG inventory
Original 2002 GHG inventory
2002 GHG inventory and updated coal ESI factors
Review of Carbon Emission Factors
% change
-8.73
-8.29
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Solid fuels 3
3.4.2
Coal, anthracite, coke - other sectors
Tables 3.18 to 3.20 present the effects of introducing the revised coal (non-ESI
sectors), anthracite and coke CEFs into the GHG inventory.
Table 3.18: Changes in carbon emissions from total coal consumption (Mt)
Year
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
Emissions in the
original 2002 GHG
inventory
57.25
56.95
53.60
45.31
42.20
39.71
36.49
31.72
31.97
27.90
29.34
33.09
30.68
Emissions using scaled
CEFs
% change to coal
emissions
57.76
57.39
53.94
45.73
42.66
39.98
36.86
32.06
32.30
27.89
29.34
33.09
30.67
0.88
0.77
0.64
0.92
1.08
0.69
1.02
1.07
1.03
-0.04
-0.02
-0.02
-0.03
Table 3.19: Changes in carbon emissions from total anthracite consumption (Mt)
Year
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
Emissions in the
original 2002 GHG
inventory
0.97
1.32
1.06
1.57
1.62
1.18
1.12
1.04
0.78
0.73
0.75
0.90
0.65
Review of Carbon Emission Factors
Emissions using scaled
CEFs
% change to anthracite
emissions
0.97
1.32
1.06
1.57
1.62
1.19
1.13
1.05
0.79
0.73
0.75
0.91
0.66
0.00
0.00
-0.30
-0.30
0.00
1.19
0.89
0.89
1.49
-0.28
0.00
0.89
0.89
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Solid fuels 3
Table 3.20: Changes in carbon emissions from total coke consumption (Mt)
Year
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
Emissions in the
original 2002 GHG
inventory
2.17
1.81
1.88
1.63
1.45
1.24
1.32
1.10
1.09
1.39
1.36
1.30
1.01
Emissions using scaled
factors
% change to coke
emissions
1.38
1.04
1.16
0.90
0.70
0.46
0.50
0.25
0.27
0.62
0.64
0.70
0.48
-36.10
-42.51
-38.47
-44.54
-51.70
-62.82
-62.17
-77.11
-74.72
-55.60
-53.04
-46.24
-52.72
Although the CEFs for coke remained unaltered from those given in the 2002 GHG
inventory, emissions have changed due to the assumptions made about the carbon
contents of other fuels. The change arises for coke used in blast furnaces and also for
coal use in coke ovens. The important point about these source/fuel combinations is
that they are artificial devices introduced into the UK GHG inventory many years ago to
ensure that carbon balances for processes in steelworks balanced correctly. For
example, coke ovens involve carbon input as coal and carbon output as coke, breeze
and coke oven gas. The carbon content of these inputs/outputs was always fixed and
the carbon would never balance. A correction was therefore applied in the form of the
two source/fuel combinations, one for the coke oven carbon balance and one for the
blast furnace carbon balance. These corrections are, effectively the difference between
two large but similar numbers and so even a small percentage change in one of these
large numbers leads to a large percentage change in the correction.
This methodology will be updated in future versions of the GHG inventory in order to
eliminate the need for these corrections. Adopting this approach would not alter the
overall UK carbon emission but would change the detailed allocation of emissions to
individual sources, providing more accurate allocation.
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Solid fuels 3
3.4.3
Petroleum coke
Table 3.21 displays the changes in emissions caused by the update of the petroleum
coke carbon emission factors.
Table 3.21: Changes in carbon emissions from total petroleum coke consumption (Mt)
Year
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
3.4.4
Emissions in the
original 2002 GHG
inventory
0.78
0.83
1.28
1.38
1.39
1.62
1.76
1.72
1.55
1.35
1.27
0.93
1.09
Emissions using UKPIA
and cement industry
(2004) CEFs
0.91
0.97
1.44
1.55
1.55
1.81
1.95
1.91
1.74
1.53
1.44
1.04
1.22
% change
16.25
16.25
12.70
12.23
11.27
11.41
10.64
11.35
12.05
13.44
12.78
11.38
11.18
Overall change to carbon emissions resulting from revisions to the
CEFs of the solid fuels
Table 3.22 displays the gross overall emission changes in carbon emissions caused by
updates to the solid fuel factors in the 2002 GHG inventory. The effect of introducing
the revised solid fuel CEFs is to increase emissions of carbon from the inventory,
across the time series, by approximately 1% for each year.
Table 3.22: Overall emission changes (gross) caused by revisions to the CEFs of the
solid fuels (MtC)
Year
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
Emissions in the
original 2002 GHG
inventory
164.63
165.66
161.62
157.45
156.26
153.83
159.35
152.65
153.46
151.13
152.17
155.75
150.26
Emissions using updated
solid fuel factors
% change
165.87
167.40
163.01
158.64
157.31
154.12
160.29
153.73
154.89
151.82
152.98
157.16
151.84
0.75
1.05
0.86
0.76
0.67
0.19
0.59
0.71
0.93
0.45
0.53
0.91
1.05
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Gaseous fuels 4
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4
Gaseous fuels
4.1
INTRODUCTION
Within the UK the main gaseous fuel used is natural gas and this accounts for
38% of total UK carbon emissions. Smaller emissions arise from blast
furnace gas (2% of total UK carbon emissions), Other Petroleum Gas (OPG)
(1% of total UK carbon emissions) and Coke Oven Gas (less than 1% of total
carbon emissions). Table 4.1 shows the sources of natural gas within the
inventory and their overall percentage contribution to natural gas emissions in
2002.
Table 4.1:
Contribution of sources to natural gas emissions in 2002
Source
Domestic
Power stations
Other industry (combustion)
Miscellaneous
Public services
Autogenerators
Iron and steel (combustion)
Gas production
Ammonia and feedstock
Cement (fuel combustion)
Refineries(combustion)
Railways (stationary sources)
Agriculture
Lime production(combustion)
Iron and steel (blast furnaces)
SSF production
Nuclear fuel production,
Coke production
Collieries
% contribution to overall natural gas
emission
34
26
14
6
4
3
2
1
1
Minor emissions of less than 1% each arise
from these sources
The main source of emissions for both blast furnace gas and coke oven gas is
the iron and steel industry. This industry accounts for 96% of carbon
emissions from blast furnace gas and 52% of emissions from coke oven gas.
The majority of the remaining emissions from coke oven gas arise from coke
production.
The main source of emissions from OPG is from combustion at refineries.
This accounts for 88% of emissions from OPG.
4.2
CEFs OF GASEOUS FUELS USED IN THE 2002 GHG
INVENTORY
4.2.1
Natural Gas
The current carbon emission factor for natural gas is 1.501 kt/Mth (52.16 t
CO2/TJ gross) and was supplied by British Gas in 1992. This emission factor
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Gaseous fuels 4
=
is applied across the time series from 1990 to 2002 for all the sources listed in
Table 4.1.
4.2.2
Coke oven gas
The current coke oven gas carbon emission factor was supplied by British
coal in 1989. The factor used is 1.599 kt/Mt and is applied across the whole
time series of emissions.
4.2.3
Blast furnace gas
The current blast furnace gas carbon emission factor was supplied by British
Coal in 1989. The factor used is 6.273 kt/Mt and is applied across the whole
time series of emissions.
4.2.4
Other petroleum gas (OPG)
The current OPG carbon emission factor was supplied by the UK Petroleum
Institute Association (UKPIA) in 1989. The factor used is 1.627 kt/Mtherm
and is applied across the whole time series of emissions.
4.3
REVISED CEFs
4.3.1
Fraction of fuel unoxidised after combustion
The CEFs in this section account for the carbon left unoxidised after
combustion. The assumption is that the oxidation is 100%.
4.3.2
Natural gas
A time series of carbon emission factors (CEF) for natural gas was obtained
from Transco (2004). Data was provided for the years 1990, 1994, 1996,
1998, 1999, 2000, 2002, 2003 and is displayed in Table 4.2.
Table 4.2:
Year
1990
1994
1996
1998
1999
2000
2002
2003
Natural gas emission factors (Transco, 2004)
Mean Carbon Emission Factor tCO2/TJ(gross)
50.37
50.76
50.99
51.25
51.48
51.28
51.39
51.45
Details of the calculation procedures can be found in Transco (2004bMPR039). Transco (2004a-MPR046) state that there are two main factors
that contribute to the variability in annual mean CEFs. Firstly, the increasing
influence over time from gas entering the supply network at the St Fergus
entry point in Scotland, and secondly, the increasing CEF at this point. It is
suggested that the gas quality changes observed at this point reflect changes
in the economics of ethylene production and prevailing international factors
(e.g. 1990 Gulf War).
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Gaseous fuels 4
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The inventory requires emission factors for every year from 1990-2002. We
concluded that the best method to derive CEFs for the years 1991, 92, 93, 95,
97 and 2001, was to linearly interpolate between the data for the years
provided. This decision was made based on the observation that there was a
statistically significant correlation between the year and the CEF measured in
that year; see Figure 4.1.
Figure 4.1: Variation in the natural gas CEF with time (data supplied by
Transco, 2004a)
51.8
CEF (tCO2/TJ)
51.6
y = 0.0858x - 120.31
R2 = 0.8972
51.4
51.2
51
50.8
50.6
50.4
50.2
1988
1990
1992
1994
1996
1998
2000
2002
2004
year
Linearly interpolating between the data supplied by Transco provided the
following CEFs for the intervening years:
Table 4.3:
Year
1991
1992
1993
1995
1997
2001
Linearly interpolated emission factors for natural gas
CEF (tCO2/TJ (gross))
50.47
50.57
50.66
50.88
51.12
51.34
Within the inventory, data is held in ktC/Mtherm for natural gas. The CEFs
were converted from TJ to Therms using the following expression:
CEF ktC/Mth = ((A*(12/44))/0.009478)/1000
where
A = CEF tCO2/TJ (gross)
0.009478 = Conversion factor for TJ to Mtherms (DTI, 2003)
The time series resulting from this calculation is shown in Table 4.4.
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Gaseous fuels 4
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Table 4.4:
Year
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
4.3.3
CEFs for natural gas (ktC/Mtherm)
CEF ktC/Mtherm
1.4494
1.4522
1.4550
1.4578
1.4606
1.4639
1.4672
1.4710
1.4747
1.4813
1.4756
1.4772
1.4787
1.4805
Coke oven gas
Updated emission factors for coke oven gas were obtained from Corus
(2004). The factor recommended for use across the time series was
1.203 kt/Mt.
4.3.4
Blast furnace gas
Updated emission factors for blast furnace gas were obtained from Corus
(2004). The factor recommended for use across the time series was
7.459 kt/Mt.
4.3.5
Other petroleum gas
An updated emission factor for other petroleum gas was obtained from UKPIA
(2004). The factor recommended for use across the time series was
1.64398 kt/Mtherm.
4.4
EFFECT OF REVISING THE CEFs FOR GASEOUS
FUELS ON CARBON EMISSIONS
4.4.1
Natural gas
Tables 4.5 to 4.7 display the results of introducing the new CEFs (Transco,
2004) for natural gas into the 2002 GHG inventory. Table 4.5 shows the
difference between natural gas emissions before and after the CEF update
with Table 4.7 showing the overall effect the update had on overall carbon
emissions in the UK.
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Gaseous fuels 4
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Table 4.5:
Year
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
Emissions in the
original 2002 GHG
inventory
30.35
32.65
32.81
36.94
39.46
41.17
48.91
49.90
52.19
55.53
57.13
57.03
56.47
Table 4.6:
Year
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
Changes in carbon emissions after applying the revised natural
gas CEF, from natural gas only (Mt)
Emissions using Transco
(2004) factors
% change
29.39
31.67
31.90
36.00
38.53
41.26
47.94
49.01
51.37
54.87
56.24
56.20
55.70
-3.17
-3.01
-2.77
-2.55
-2.36
-2.16
-1.98
-1.78
-1.57
-1.19
-1.54
-1.45
-1.35
Changes to overall UK carbon emissions after applying the
revised natural gas CEF (Mt)
Emissions in the
original 2002 GHG
inventory
161.75
162.75
158.66
154.43
153.19
150.68
156.18
149.49
150.32
147.99
148.99
152.58
147.08
Emissions using Transco
(2004) factors
% change
160.79
161.77
157.76
153.49
152.25
149.77
155.21
148.60
149.50
147.33
148.10
151.76
146.31
-0.60
-0.60
-0.57
-0.61
-0.61
-0.60
-0.62
-0.60
-0.55
-0.45
-0.59
-0.54
-0.52
Table 4.7 displays the overall percentage changes in carbon emissions
between 1990 and 2002, and the change in the carbon emissions after the
revised natural gas CEF has been applied. The effect of introducing the new
CEF is negligible.
Table 4.7:
Percentage change in overall carbon emissions between 1990
and 2002 after introducing the revised natural gas CEF
4.4.1.1
Database
Original 2002 GHG inventory
2002 GHG inventory and updated natural gas CEF
factors
Review of Carbon Emission Factors
% change
-9.07%
-9.00%
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Gaseous fuels 4
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The tables in the following sections set out the effects of introducing the CEFs
for selected gaseous fuels into the 2002 GHG inventory.
4.4.2
Blast furnace gas
Table 4.8:
Year
Changes to carbon emissions following revision of the blast
furnace gas CEF (MtC)
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
Emissions in the
original 2002 GHG
inventory
4.14
4.08
3.82
3.83
3.97
4.13
4.34
4.47
4.29
4.10
3.82
3.18
2.83
4.4.3
Coke oven gas
Table 4.9:
Year
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
Emissions using Corus
(2004) CEFs
% change
4.92
4.85
4.54
4.55
4.72
4.91
5.16
5.32
5.11
4.87
4.54
3.78
3.36
18.91
18.91
18.91
18.91
18.91
18.91
18.91
18.91
18.91
18.91
18.91
18.91
18.91
Changes to carbon emissions following revision of the coke
oven gas CEF (MtC)
Emissions in the
original 2002 GHG
inventory
0.95
0.87
0.79
0.75
0.74
0.71
0.78
0.77
0.76
0.71
0.73
0.64
0.53
Review of Carbon Emission Factors
Emissions using Corus
(2004) CEFs
% change
0.72
0.66
0.60
0.57
0.56
0.54
0.60
0.58
0.58
0.54
0.55
0.48
0.41
-24.18
-24.20
-24.19
-24.15
-24.18
-24.03
-23.13
-23.78
-23.12
-24.33
-24.63
-24.28
-24.24
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Gaseous fuels 4
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4.4.4
Other petroleum gas (OPG)
Table 4.10: Changes to carbon emissions following revision of the OPG
CEF (MtC)
Year
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
4.4.5
Emissions in the
original 2002 GHG
inventory
2.39
2.37
2.35
2.52
2.61
2.73
2.74
2.53
2.40
2.36
2.39
2.27
2.03
Emissions using UKPIA
(2004) CEFs
% change
2.42
2.40
2.38
2.54
2.63
2.75
2.77
2.56
2.43
2.38
2.41
2.29
2.05
1.04
1.04
1.04
1.04
1.04
1.04
1.04
1.04
1.04
1.04
1.04
1.04
1.04
Overall change to carbon emissions resulting from revisions to
the CEFs of the gaseous fuels
Table 4.11 shows the overall effect of updating all the CEFs for gaseous fuels
on the carbon emissions from the 2002 GHG inventory. The effect of
introducing the revised gaseous fuel CEFs is to slightly decrease emissions of
carbon from the inventory, across the time series, by no more than 0.25% with
the greatest effect in the early and later years of the inventory. The effect of
revising the gaseous fuel CEFs is much smaller than revising the CEFs of the
solid fuels.
Table 4.11: Overall effect on UK carbon emission totals using updated
gaseous fuels CEFs (MtC)
Year
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
Emissions in the
original 2002 GHG
inventory
161.75
162.75
178.66
154.43
153.19
150.68
156.18
149.49
150.32
147.99
148.99
152.58
147.08
Emissions using updated
gaseous factors
% change
161.36
162.35
158.31
154.05
152.85
150.41
155.88
149.29
150.15
147.95
148.67
152.23
146.74
-0.24
-0.24
-0.22
-0.24
-0.22
-0.18
-0.19
-0.13
-0.11
-0.02
-0.21
-0.23
-0.23
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Liquid fuels 5
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5
Liquid fuels
5.1
INTRODUCTION
There are a number of liquid fuels used within the UK. The major liquid fuels
that are used are petrol, DERV, gas oil, burning oil and fuel oil. The
percentage contribution to UK emissions listed in Table 2.2. Other fuels that
are used include Aviation Turbine Fuel (ATF), premium burning oil, waste oils,
aviation spirit, LPG and naphtha. Table 5.1 displays the main sectors using
each fuel and their percentage contribution to overall emissions from that fuel.
Table 5.1:
Sources of carbon from liquid fuels in the UK
Fuel
Source
Petrol
Road transport
Other industry (off road)
Road transport
Domestic house and garden
Power Stations
Refineries (combustion)
Public Services
Miscellaneous
Other industry (combustion)
Iron and Steel (combustion)
Coastal
Refineries
Miscellaneous
Public services
Domestic
Agriculture
Other industry (combustion)
Iron and Steel (combustion)
Shipping, Naval
Railways
Coastal
Fishing
Agricultural power units
Other industry off-road
Domestic
Other Industry (Combustion)
Railways
Public Services
Miscellaneous
Domestic Aviation
Military aviation
Domestic Aviation
Domestic
Refineries (combustion)
Gas Separation Plant (combustion)
Domestic
Other Industry (combustion)
Road Transport
Refineries (combustion)
Cement (fuel combustion)
DERV
Fuel oil
Gas oil
Burning oil
Aviation turbine fuel
Aviation spirit
Burning oil (premium)
LPG
Naphtha
Waste oils
Review of Carbon Emission Factors
% contribution to overall fuel emission
in UK reported in national totals to the
IPCC
99
1
99.9
0.1
20
53
4
2
14
5
1
2
6
9
3
2
32
3
4
4
8
1
4
19
71
28
0.3
0.3
0.3
55
45
100
100
1
1
29
61
8
100
100
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Liquid fuels 5
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5.2
CEFs OF LIQUID FUELS USED IN THE 2002 GHG
INVENTORY
All the current factors for liquid fuels were supplied to AEA Technology by the
United Kingdom Petroleum Industry Association (UKPIA) in 1989. Table 5.2
shows each liquid fuel in the inventory and its corresponding emission factor.
These emission factors apply across the time series of emissions from 1990
to 2002 inclusive.
Table 5.2:
Carbon emission factors for liquid fuels in the 2002 GHG
inventory
Fuel
Aviation spirit
Aviation turbine fuel
Burning oil
Burning oil premium
DERV
Fuel oil
Gas oil
LPG
Naphtha
Petrol
Waste oils
Current carbon emission factor (ktC/Mt)
859
859
859
859
857
850
857
1.712ktC/Mtherm
940
855
859
These factors are applied across all sources for each fuel (as listed in
Table 5.1).
5.3
REVISED CEFs
Updated emission factors for liquid fuels were obtained from UKPIA (2004)
who carried out a survey of the carbon contents of selected fuels. Table 5.3
shows the updated factors that were supplied. The CEFs of fuels not included
in this list remain unchanged and were left equal to the values in the
2002 GHG inventory. A summary of the reasons for changes to the factors is
given in the notes below the table and more detailed information is given in
UKPIA (2004).
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Liquid fuels 5
=
Table 5.2:
Fuel
Naphtha
Aviation spirit
Diesel
Gas oil
Fuel oil
Updated emission factors for liquid fuels (KteC/Mte), as supplied by UKPIA (2004)
1990
854
853
864
869
867
1991
854
853
864
869
868
1992
854
853
864
869
865
1993
854
853
864
869
865
1994
854
853
864
869
865
1995
854
853
864
869
865
1996
854
853
864
869
865
1997
854
853
864
870
868
1998
854
853
864
870
871
1999
854
853
863
870
874
2000
854
853
863
870
875
2001
854
853
863
870
875
2002
854
853
863
870
877
2003
854
853
863
870
879
Notes:
• Naphtha and aviation spirit assumed to be constant and based on UKPIA 2004 survey results
• Petrol is assumed to be constant and unchanged from current CEF assumed, and these assumptions are supported by UKPIA 2004 survey results
• Diesel is corrected for changes in sulphur content and density over time using smoothed sulphur contents from the annual UKPIA survey of sulphur
contents and density from DTI DUKES
• Gas oil and fuel oil corrected for changes in sulphur content over time using smoothed sulphur contents from the annual UKPIA survey of sulphur
contents
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Liquid fuels 5
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5.3.1
Fraction of fuel unoxidised after combustion
The CEFs in this section account for the carbon left unoxidised after
combustion.
A short review was completed to determine what a suitable oxidation factor
should be. During this review, we
contacted the UK Petroleum Industries Association (UKPIA) to seek
their view on the appropriate oxidation factors;
considered the views of experts involved in the mobile combustion
chapter of the 2006 IPPC guidelines;
consulted with our transport sector, Tim Murrells, for his views on the
mobile combustion.
The details of this review are given in Appendix 2. We concluded that the
fraction oxidised for liquid fuels should remain at 100% across the time series,
primarily because of the uncertainty in the estimates of the fractions of fuels
unoxidised and the difficulties of generating an accurate and defensible time
series of unoxidised fractions for each fuel used in the GHG inventory from
1990 to the most current year.
5.4
EFFECT OF REVISING THE CEFs FOR LIQUID FUELS
ON CARBON EMISSIONS
The tables in the following sections set out the effects of introducing the CEFs
for liquid fuels into the 2002 GHG inventory.
5.4.1
Naphtha
Table 5.4:
Year
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
Changes to carbon emissions following revisions to the naptha
CEF (MtC)
Emissions in the
original 2002
GHG inventory
0.02
0.02
0.02
0.02
0.01
0.00
0.00
0.01
0.01
0.02
0.01
0.05
0.02
Emissions using UKPIA (2004)
naptha CEF
%
change
0.02
0.02
0.02
0.02
0.01
0.00
0.00
0.01
0.01
0.01
0.01
0.05
0.02
-9.14
-9.14
-9.14
-9.14
-9.14
-9.14
-9.14
-9.14
-9.14
-9.14
-9.14
-9.14
-9.14
Review of Carbon Emission Factors
AEA Energy & Environment
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33
Liquid fuels 5
=
5.4.2
Aviation spirit
Table 56.5: Changes to carbon emissions following revisions to the aviation
spirit CEF (MtC)
Year
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
5.4.3
Emissions in the
original 2002
GHG inventory
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.03
0.03
0.03
0.04
0.05
0.04
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
%
change
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.03
0.03
0.03
0.04
0.05
0.04
-1.38
-1.38
-1.38
-1.38
-1.38
-1.38
-1.38
-1.38
-1.38
-1.38
-1.38
-1.38
-1.38
Fuel Oil
Table 5.6:
Year
Emissions using UKPIA (2004)
aviation spirit CEF
Changes to carbon emissions following revisions to the fuel oil
CEF (MtC)
Emissions in the
original 2002
GHG inventory
11.7
11.6
10.5
9.95
8.92
7.66
7.04
5.31
4.54
3.78
2.80
3.45
3.24
Emissions using UKPIA (2004)
fuel oil CEF
%
change
12.0
11.9
10.7
10.1
9.08
7.80
7.16
5.43
4.66
3.89
2.89
3.55
3.35
2.00
2.12
1.76
1.76
1.76
1.76
1.76
2.12
2.47
2.82
2.94
2.94
3.18
Review of Carbon Emission Factors
AEA Energy & Environment
Page
34
Liquid fuels 5
=
5.4.4
Gas oil
Table 5.7:
Year
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
5.4.5
Emissions in the
original 2002 GHG
inventory
7.27
7.27
7.11
6.99
6.73
6.51
6.87
6.64
6.50
6.02
5.90
5.88
5.54
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
5.4.6
Emissions using UKPIA (2004)
gas oil CEF
% change
7.37
7.38
7.21
7.09
6.83
6.60
6.96
6.75
6.59
6.11
5.99
5.97
5.63
1.30
1.40
1.35
1.36
1.39
1.40
1.37
1.48
1.18
1.48
1.52
1.52
1.52
Diesel oil
Table 5.8:
Year
Changes to carbon emissions following revisions to the gas oil
CEF (MtC)
Changes to carbon emissions following revisions to the diesel oil
CEF (MtC)
Emissions in the
original 2002 GHG
inventory
9.13
9.16
9.54
10.1
11.0
11.5
12.3
12.8
12.9
13.2
13.3
14.0
15.1
Emissions using UKPIA (2004)
diesel oil CEF
%
change
9.20
9.24
9.62
10.2
11.1
11.6
12.4
12.9
13.0
13.3
13.4
14.1
15.2
0.82
0.82
0.82
0.82
0.82
0.82
0.82
0.82
0.82
0.70
0.70
0.70
0.70
Overall change to carbon emissions resulting from revisions to
the CEFs of the liquid fuels
Table 5.9 displays the overall effect that updating the liquid fuel CEFs has on
overall inventory carbon emissions from the 2002 GHG inventory. Introducing
the revised liquid fuel CEFs slightly increases the emissions of carbon from
Review of Carbon Emission Factors
AEA Energy & Environment
Page
35
Liquid fuels 5
=
the inventory across the time series, by no more than 0.25%, with the greatest
effect in the early years of the inventory.
Table 5.9:
Year
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
Overall effect on UK carbon emissions using updated liquid fuel
CEFs (MtC)
Emissions in the
original 2002 GHG
inventory
164.6
165.6
161.6
157.4
156.2
153.8
159.3
152.6
153.4
151.1
152.1
155.7
150.2
Review of Carbon Emission Factors
Emissions using UKPIA (2004)
CEFs
% change
165.0
166.0
161.9
157.8
156.6
154.1
159.6
152.9
153.7
151.4
152.4
156.0
150.5
0.24
0.25
0.22
0.22
0.22
0.21
0.20
0.21
0.20
0.19
0.17
0.18
0.19
AEA Energy & Environment
Page
36
Overall effect on carbon emissions 6
=
6
Overall effect on carbon emissions of the
revised CEFs
The following table displays the overall emissions as a result of revisions to all
the solid, liquid and gaseous fuels documented in the report. Emissions are
presented in MtC and are gross values. The overall effect is to increase the
carbon emissions across the time series, by 1.3% in 1990 (the base year for
the sources and fuels considered in this report), and by 1.5% in 2002.
Table 6.1:
Year
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
% change
1990-2002
Overall effect on UK carbon emissions after applying all the
revised CEFs (MtC)
Emissions in the
original 2002 GHG
inventory
164.6
165.6
161.6
157.4
156.2
153.8
159.3
152.6
153.4
151.1
152.1
155.7
150.2
-8.73%
Emissions
using updated
factors
165.8
167.4
163.0
158.6
157.3
154.1
160.3
153.8
155.0
152.0
152.9
157.0
151.7
-8.50%
% change
Actual
change
0.76
1.07
0.86
0.75
0.67
0.22
0.60
0.78
1.02
0.62
0.50
0.86
1.02
1.25
1.77
1.40
1.17
1.05
0.34
0.96
1.19
1.57
0.93
0.76
1.34
1.52
Tables 6.2 and 6.3 display the emissions, according to fuel type, for the
original 2002 GHG inventory, and for 2002 GHG inventory with the updated
carbon emission factors. Table 6.4 displays the percentage change overall,
and by fuel type.
The overall effect of introducing the revised CEFs into the inventory was to
slightly increase carbon emission across the time series. Emissions of carbon
in 1990 increased by 0.8%, and by 1.0% in 2002.
Review of Carbon Emission Factors
AEA Energy & Environment
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Overall effect of the revised CEFs 6
=
Table 6.2:
Carbon emissions in the original 2002 GHG inventory (MtC)
IPCC Fuel
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
Anthracite
Aviation Gasoline
Blast Furnace Gas
Coke Oven Coke
Coke Oven Gas
Coking Coal
Colliery Methane
Gas/Diesel Oil
Gas Works Gas
Jet Gasoline
Liquefied Petroleum Gas
Lubricants
Motor Gasoline
Municipal Solid Waste
Naphtha
Natural Gas
Non-Fuel Combustion
Non IPCC
Orimulsion
Other Bituminous Coal
Other Kerosene
Other Oil
Patent Fuel
Petroleum Coke
Refinery Gas
Residual Fuel Oil
Scrap Tyres
0.97
0.02
4.14
2.17
0.95
0.45
0.06
16.40
0.00
1.63
0.88
0.28
20.79
0.22
0.02
30.35
10.63
0.08
0.09
56.80
1.77
0.02
0.94
0.78
2.39
11.78
0.00
1.32
0.02
4.08
1.81
0.87
0.38
0.05
16.44
0.00
1.33
1.02
0.26
20.54
0.22
0.03
32.65
9.83
0.08
0.25
56.57
2.05
0.03
0.93
0.83
2.37
11.68
0.00
1.06
0.02
3.82
1.88
0.79
0.28
0.05
16.65
0.00
1.33
0.91
0.27
20.56
0.22
0.03
32.81
9.56
0.08
0.77
53.31
2.12
0.04
0.84
1.28
2.35
10.59
0.00
1.57
0.02
3.83
1.63
0.75
0.29
0.04
17.11
0.00
1.40
0.93
0.28
20.32
0.22
0.02
36.94
9.09
0.08
0.85
45.02
2.25
0.05
0.90
1.38
2.52
9.95
0.00
1.62
0.03
3.97
1.45
0.74
0.29
0.04
17.80
0.00
1.37
0.99
0.28
19.53
0.22
0.02
39.46
9.66
0.08
0.73
41.91
2.28
0.09
0.75
1.39
2.61
8.92
0.05
1.18
0.03
4.13
1.24
0.71
0.35
0.03
18.04
0.00
1.38
0.97
0.31
18.77
0.22
0.00
42.17
8.95
0.08
0.76
39.35
2.38
0.09
0.60
1.62
2.73
7.66
0.06
1.12
0.03
4.34
1.32
0.78
0.32
0.03
19.18
0.00
1.38
1.09
0.30
19.16
0.22
0.00
48.91
9.15
0.08
0.52
36.17
2.87
0.11
0.67
1.76
2.74
7.04
0.09
1.04
0.03
4.47
1.10
0.77
0.40
0.03
19.48
0.00
1.33
1.00
0.30
19.02
0.14
0.02
49.90
9.01
0.08
0.11
31.33
2.87
0.07
0.50
1.72
2.53
5.31
0.09
0.78
0.03
4.29
1.09
0.76
0.39
0.02
19.47
0.00
1.34
1.00
0.28
18.68
0.20
0.02
52.19
9.07
0.08
0.00
31.58
3.07
0.06
0.50
1.55
2.40
4.54
0.06
0.73
0.04
4.10
1.39
0.71
0.49
0.02
19.31
0.00
1.31
0.96
0.27
18.63
0.19
0.02
55.53
8.75
0.08
0.00
27.41
3.12
0.07
0.45
1.35
2.36
3.78
0.05
0.75
0.04
3.82
1.36
0.73
0.37
0.02
19.30
0.00
1.26
0.92
0.28
18.47
0.20
0.02
57.13
8.17
0.08
0.00
28.97
3.30
0.09
0.41
1.27
2.39
2.80
0.02
0.90
0.05
3.18
1.30
0.64
0.46
0.02
19.95
0.00
1.31
1.01
0.28
17.90
0.22
0.05
57.03
7.95
0.08
0.00
32.63
3.65
0.11
0.38
0.93
2.27
3.45
0.02
0.65
0.04
2.83
1.01
0.53
0.38
0.02
20.67
0.00
1.37
0.88
0.29
16.89
0.24
0.03
56.47
7.45
0.07
0.00
30.29
3.31
0.11
0.33
1.09
2.03
3.24
0.02
164.6
165.7
161.6
157.4
156.3
153.8
159.3
152.6
153.5
151.1
152.2
155.8
150.3
Total emissions
(ktC)
Review of Carbon Emission Factors
AEA Energy & Environment
Page
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Overall effect of the revised CEFs 6
=
Table 6.3:
Carbon emissions after introducing CEFs for solid, liquid and gaseous fuels (MtC) into the 2002 GHG inventory
IPCC Fuel
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
Anthracite
Aviation Gasoline
Blast Furnace Gas
Coke Oven Coke
Coke Oven Gas
Coking Coal
Colliery Methane
Gas/Diesel Oil
Gas Works Gas
Jet Gasoline
Liquefied Petroleum Gas
Lubricants
Motor Gasoline
Municipal Solid Waste
Naphtha
Natural Gas
Non-Fuel Combustion
Non IPCC
Orimulsion
Other Bituminous Coal
Other Kerosene
Other Oil
Patent Fuel
Petroleum Coke
Refinery Gas
Residual Fuel Oil
Scrap Tyres
0.97
0.02
4.92
1.38
0.72
0.74
0.06
16.57
0
1.63
0.88
0.28
20.79
0.22
0.02
29.39
10.63
0.08
0.09
58.41
1.77
0.02
0.94
0.91
2.42
12.02
0
1.32
0.02
4.85
1.04
0.66
0.65
0.05
16.62
0
1.33
1.02
0.26
20.54
0.22
0.03
31.67
9.83
0.08
0.25
58.69
2.05
0.03
0.93
0.97
2.4
11.93
0
1.06
0.02
4.54
1.16
0.6
0.52
0.05
16.82
0
1.33
0.91
0.27
20.56
0.22
0.02
31.9
9.56
0.08
0.77
55.03
2.12
0.04
0.84
1.44
2.38
10.78
0
1.57
0.02
4.55
0.9
0.57
0.52
0.04
17.29
0
1.4
0.93
0.28
20.32
0.22
0.02
36
9.09
0.08
0.85
46.55
2.25
0.05
0.9
1.55
2.54
10.13
0
1.62
0.02
4.72
0.7
0.56
0.52
0.04
17.98
0
1.37
0.99
0.28
19.53
0.22
0.01
38.53
9.66
0.08
0.73
43.32
2.28
0.09
0.75
1.55
2.63
9.08
0.05
1.19
0.02
4.91
0.46
0.54
0.56
0.03
18.23
0
1.38
0.97
0.31
18.77
0.22
0
41.26
8.95
0.08
0.76
40.02
2.38
0.09
0.6
1.81
2.75
7.8
0.06
1.13
0.03
5.16
0.5
0.6
0.65
0.03
19.37
0
1.38
1.09
0.3
19.16
0.22
0
47.94
9.15
0.08
0.52
37.4
2.87
0.11
0.67
1.95
2.77
7.16
0.09
1.05
0.03
5.32
0.25
0.58
0.73
0.03
19.69
0
1.33
1
0.3
19.02
0.14
0.0.1
49.01
9.01
0.08
0.11
32.72
2.87
0.07
0.5
1.91
2.56
5.43
0.09
0.79
0.03
5.11
0.27
0.58
0.73
0.02
19.68
0
1.34
1
0.28
18.68
0.2
0.01
51.37
9.07
0.08
0
33.28
3.07
0.06
0.5
1.74
2.43
4.66
0.06
0.73
0.04
4.87
0.62
0.54
0.52
0.02
19.49
0
1.31
0.96
0.27
18.63
0.19
0.02
54.87
8.75
0.08
0
28.66
3.12
0.07
0.45
1.53
2.38
3.89
0.05
0.75
0.04
4.54
0.64
0.55
0.39
0.02
19.48
0
1.26
0.92
0.28
18.47
0.2
0.02
56.24
8.17
0.08
0
30.32
3.3
0.09
0.41
1.44
2.41
2.89
0.02
0.91
0.05
3.78
0.7
0.48
0.49
0.02
20.14
0
1.31
1.01
0.28
17.9
0.22
0.05
56.2
7.95
0.08
0
34.5
3.65
0.11
0.38
1.04
2.29
3.55
0.02
0.66
0.04
3.36
0.48
0.41
0.41
0.02
20.86
0
1.37
0.88
0.29
16.89
0.24
0.02
55.7
7.45
0.07
0
32.25
3.31
0.11
0.33
1.22
2.05
3.35
0.02
165.9
167.4
163.0
158.6
157.3
154.2
160.3
153.8
155.0
152.1
152.9
157.1
151.8
Total emissions
(ktC)
Review of Carbon Emission Factors
AEA Energy & Environment
Page
39
Overall effect of the revised CEFs 6
=
Table 6.3:
Percentage change in carbon emissions, according to fuel, after introducing the revised CEFs into the 2002 GHG
inventory
IPCC Fuel
Anthracite
Aviation Gasoline
Blast Furnace Gas
Coke Oven Coke
Coke Oven Gas
Coking Coal
Colliery Methane
Gas/Diesel Oil
Gas Works Gas
Jet Gasoline
Liquefied Petroleum Gas
Lubricants
Motor Gasoline
Municipal Solid Waste
Naphtha
Natural Gas
Non-Fuel Combustion
Non IPCC
Orimulsion
Other Bituminous Coal
Other Kerosene
Other Oil
Patent Fuel
Petroleum Coke
Refinery Gas
Residual Fuel Oil
Scrap Tyres
Overall % change
1990
1991
1992
1993
1994
1995
1996
1997
0.00
-1.38
18.90
-36.09
-24.18
63.22
0.00
1.03
0.00
0.00
0.00
0.00
0.00
0.00
-9.14
-3.16
0.00
0.00
0.00
2.82
0.00
0.00
0.00
16.25
1.044
2.00
-
0.00
-1.38
18.90
-42.51
-24.20
68.63
0.00
1.07
0.00
0.00
0.00
0.00
0.00
0.00
-9.14
-3.00
0.00
0.00
0.00
3.74
0.00
0.00
0.00
16.25
1.044
2.11
-
-0.29
-1.38
18.90
-38.47
-24.19
84.31
0.00
1.04
0.00
0.00
0.00
0.00
0.00
-9.14
-2.76
0.00
0.00
0.00
3.21
0.00
0.00
0.00
12.70
1.044
1.76
-
-0.29
-1.38
18.90
-44.53
-24.14
78.27
0.00
1.04
0.00
0.00
0.00
0.00
0.00
-9.14
-2.55
0.00
0.00
0.00
3.40
0.00
0.00
0.00
12.23
1.044
1.76
-
0.00
-1.38
18.90
-51.70
-24.17
75.87
0.00
4.03
0.00
0.00
0.00
0.00
0.00
-9.14
-2.36
0.00
0.00
0.00
3.36
0.00
0.00
0.00
11.27
1.044
1.76
0.00
1.19
-1.38
18.90
-62.81
-24.03
59.96
0.00
1.02
0.00
0.00
0.00
0.00
0.00
-2.15
0.00
0.00
0.00
1.69
0.00
0.00
0.00
11.41
1.044
1.76
0.00
0.89
-1.38
18.90
-62.17
-23.12
104.92
0.00
1.01
0.00
0.00
0.00
0.00
0.00
-1.98
0.00
0.00
0.00
3.40
0.00
0.00
0.00
10.64
1.044
1.76
0.00
0.89
-1.38
18.90
-77.11
-23.77
84.47
0.00
1.04
0.00
0.00
0.00
0.00
0.00
-9.14
-1.78
0.00
0.00
0.00
4.43
0.00
0.00
0.00
11.34
1.044
2.11
0.00
0.76%
Review of Carbon Emission Factors
1.06%
0.86%
0.74%
0.67%
0.22%
AEA Energy & Environment
0.60%
0.78%
1998
1.49
-1.39
18.91
-74.72
-24.12
85.50
0.00
1.04
0.00
0.00
0.00
0.00
0.00
-9.15
-1.57
0.00
0.00
5.40
0.00
0.00
0.00
12.05
1.04
2.47
0.00
1.02%
1999
-0.30
-1.39
18.91
-55.60
-24.33
6.59
0.00
0.94
0.00
0.00
0.00
0.00
0.00
-9.15
-1.19
0.00
0.00
4.55
0.00
0.00
0.00
13.44
1.04
2.82
0.00
0.62%
2000
0.00
-1.39
18.91
-53.04
-24.62
4.45
0.00
0.95
0.00
0.00
0.00
0.00
0.00
-9.15
-1.54
0.00
0.00
4.68
0.00
0.00
0.00
12.78
1.04
2.94
0.00
0.50%
Page
2001
0.89
-1.39
18.91
-46.24
-24.28
6.03
0.00
0.94
0.00
0.00
0.00
0.00
0.00
-9.15
-1.45
0.00
0.00
5.73
0.00
0.00
0.00
11.38
1.04
2.94
0.00
0.86%
40
2002
0.89
-1.39
18.91
-52.72
-24.24
6.31
0.00
0.92
0.00
0.00
0.00
0.00
0.00
-9.15
-1.35
0.00
0.00
6.45
0.00
0.00
0.00
11.18
1.04
3.18
0.00
1.02%
References 7
=
7
References
Baggott, S. L., Brown, L., Milne, R., Murrells, T.P., Passant, N. and
Watterson, J.D. (2004). UK Greenhouse Gas Inventory, 1990 to 2002.
Annual Report for submission under Framework Convention on Climate
Change. National Environmental Technology Centre, AEA Technology
Centre, AEAT/ENV/R/1702.
British Gas (1992) Personal communication with Geoff Salway.
British Coal (1989) Personal communication with Simon Eggleston. British
Coal Research, Bretby, Derbyshire, UK.
Corus (2004) Personal communication. Peter Quinn.
DTI DUKES (2004), Digest of United Kingdom Energy Statistics 2004, TSO,
London 123 Kingsway London, WC2B 6PQ, UK.
IPCC, (1997a), IPCC Revised 1996 Guidelines for National Greenhouse Gas
Inventories, Volume 1, Greenhouse Gas Inventory Reporting Instructions,
IPCC WGI Technical Support Unit, Hadley Centre, Meteorological Office,
Bracknell, UK.
IPCC, (1997b), IPCC Revised 1996 Guidelines for National Greenhouse Gas
Inventories, Volume 2, Greenhouse Gas Inventory Workbook, IPCC WGI
Technical Support Unit, Hadley Centre, Meteorological Office, Bracknell, UK.
IPCC, (1997c), IPCC Revised 1996 Guidelines for National Greenhouse Gas
Inventories, Volume 3, Greenhouse Gas Inventory Reference Manual, IPCC
WGI Technical Support Unit, Hadley Centre, Meteorological Office, Bracknell,
UK.
IPCC, (2000), Good Practice Guidance and Uncertainty Management in
National Greenhouse Gas Inventories, ed. Penman, J, Kruger, D, Galbally, I,
et al, IPCC National Greenhouse Gas Inventories Programme, Technical
Support Programme Technical Support Unit, Institute for Global
Environmental Strategies, Hayama, Kanagawa, Japan.
Joslin, A., Rodgers, I., Salway, G. and Tabberer, R. (2004) Relating fuel
consumption to CO2 emissions. Review and recommendations for power
station fuel and plant parameters for use in the DTI power station model. AEP
Report EncC 159/04.
Transco (2004a) Measurement and Process Report: MPR046. Estimation of
Carbon Dioxide Emission Factors for UK Natural Gas 1990-2003. Safety &
Engineering report. Dave Lander, Standards Manager (Gas Quality), UK
Distribution, National Grid (formerly Transco), National Grid House,
Warwickshire, CV34 6DA, UK.
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Page
41
References 7
=
Transco (2004b) Measurement and Process Report: MPR039. Estimation of
Carbon Dioxide Emission Factors for UK Natural Gas 2002 and 2003. Safety
& Engineering report. Dave Lander, Standards Manager (Gas Quality), UK
Distribution, National Grid (formerly Transco), National Grid House,
Warwickshire, CV34 6DA, UK.
Quick (2004). Personal communication. Will Quick, Joint Environmental
Programme (JEP), funded by the Association of Electricity Producers (AEP).
Power Technology, Ratcliffe on Soar, Nottingham, NG11 0EE, UK.
Rushworth (2004) Personal communication. Jim Rushworth, National Energy
Manager, Lafarge Cement UK, East Aberthaw, Barry, Vale of Glamorgan,
Wales, UK.
Simmons (2002) Review of the UK Greenhouse Gas Inventory CO2 from Fuel
Combustion 1990-1999. Avonlog Ltd.
UKPIA (2004) Carbon Content Of Fuels Used In The UK. Ian McPherson,
Assistant Director, UK Petroleum Industry Association, 9 Kingsway, London,
WC2B 6XF, UK.
UKPIA (1989) Personal communication with Simon Eggleston. UK Petroleum
Industry Association, 9 Kingsway, London, WC2B 6XF, UK.
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42
Acknowledgements 8
=
8
Acknowledgements
We are grateful for the help of the following people during the course of this
work programme; apologies for any omissions.
•
Achur, James (UK DTI)
•
Allen, Chris (TRANSCO - now National Grid UK)
•
Austwick, Caroline (Defra)
•
Boyle, Stephen (SEPA)
•
Cunningham, Mike (SEPA)
•
Dodwell, Chris (UK Defra)
•
Donaldson, Susan (UK Defra, Climate, Energy, Science and Analysis)
•
Gemill, Rob (EA)
•
Hitchin, Roger (Buildings Research Establishment, BRE)
•
JEP programme members
•
Jones, Haydn (Netcen, EA)
•
Lampert, Roger (DTI)
•
Lander, Dave (TRANSCO - now National Grid UK)
•
Maier, Margaret (DTI)
•
McGlen, Chris (UK Coal)
•
McPherson, Ian (UKPIA)
•
Penman, Jim (UK Defra, Climate, Energy, Science and Analysis)
•
Prior, Phil (Defra)
•
Pryor, Phil (TRANSCO - now National Grid UK)
•
Quick, Will (Joint Environmental Programme, E.ON Group)
•
Rushworth, Jim (Lafarge Cement)
•
Salway, Geoff (RWE Innogy plc)
•
Tauhid, Sayeeda (UK Defra)
•
Watson, Malcolm (UKPIA)
•
Wilson, Dave (DTI)
•
Wilson, Dave (UK DTI)
•
Young, Martin (UK DTI)
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Appendix 1
=
Appendix 1
A1.1
BUNKER EMISSIONS
International shipping and aviation emissions are not included in national total
emissions, but are submitted to the IPCC annually. Modifications to the CEFs
will affect the emissions from fuels consumed by international shipping and
aviation, and for completeness, the revised bunker emissions are presented in
this Appendix.
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Appendix 1
=
Table A1.1.1:
IPCC
International bunker emissions (MtC)
IPCC Fuel
International Gas/Diesel Oil
Marine
International Residual Fuel Oil
Marine
Aviation
Jet Gasoline
Bunkers
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
Emissions in 2002 Greenhouse Gas Inventory
0.59
0.63
0.70
0.66
0.75
0.64
0.72
0.66
0.96
0.73
0.72
1.18
1.09
1.11
1.12
0.94
1.15
1.24
1.53
1.43
1.00
0.79
4.03
3.97
4.39
4.70
4.88
5.20
5.53
5.89
6.59
7.22
8.02
0.74
0.74
1.03
0.82
7.22
8.02
Emissions in Carbon Emissions Factor modified Greenhouse Gas Inventory
International Gas/Diesel Oil
0.60
0.64
0.70
0.67
0.73
0.65
0.73
0.67
0.97
Marine
International Residual Fuel Oil
1.21
1.12
1.13
1.14
0.96
1.17
1.26
1.56
1.46
Marine
Aviation
Jet Gasoline
4.03
3.97
4.39
4.70
4.88
5.20
5.53
5.89
6.59
Bunkers
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Appendix 1
=
Table A1.2.2:
Coal GCV for the cement industry (GJ per tonne)
SOURCE
Cement (combustion)
•
•
•
1990
28.2
1991
28.2
1992
28.2
1993
29.5
1994
28.3
1995
27.1
1996
27.4
1997
27
1998
26.6
1999
26.7
2000
27
2001
27
2002
27
2003
27.9
2004
27.7
1990-93 and 1994-99 - DUKES GCV - Mineral products
1994 - average of 93 and 95 DUKES data
2000-2004 - Data supplied by Cement industry
Table A1.2.3:
1990
29.8
Coke GCV (GJ per tonne)
1991
29.8
Table A1.2.4:
1990
39.5
Fuel
Gas oil
Fuel oil
Petrol
DERV
Aviation
Spirit
Aviation
Turbine fuel
1993
29.8
1994
29.8
1995
29.8
1996
29.8
1997
29.8
1998
29.8
1999
29.8
2000
29.8
2001
29.8
2002
29.8
1996
39.5
1997
39.5
1998
39.5
1999
39.5
2000
39.5
2001
39.5
2002
39.5
Petroleum Coke GCV (GJ per tonne)
1991
39.5
Table A1.2.5:
1992
29.8
1992
39.5
1993
39.5
1994
39.5
1995
39.5
Liquid fuel GCVs (GJ per tonne)
Dukes class
Gas/Diesel Oil (incl
DERV)
Fuel Oil
Motor Spirit
Gas/Diesel Oil (incl
DERV)
Aviation Spirit &
Wide Cut Gasoline
Aviation Turbine
Fuel
Review of Carbon Emission Factors
1990
45.4
1991
45.4
1992
45.4
1993
45.4
1994
45.4
1995
45.4
1996
45.4
1997
45.4
1998
45.5
1999
45.6
2000
45.6
2001
45.6
2002
45.6
43.2
47
45.4
43.2
47
45.4
43.2
47
45.4
43.2
47
45.4
43.2
47
45.4
43.2
47
45.4
43.2
47
45.4
43.3
47
45.4
43.2
47
45.5
43.2
47.1
45.6
43.1
47
45.6
43.5
47.1
45.6
43.4
47.1
45.6
47.3
47.3
47.3
47.3
47.3
47.3
47.3
47.3
47.3
47.3
47.3
47.3
47.3
46.2
46.2
46.2
46.2
46.2
46.2
46.2
46.2
46.2
46.2
46.2
46.2
46.2
Page
47
AEA Energy & Environment
Appendix 1
=
Table A1.2.6:
Year
DUKES
Transco
Natural Gas GCVs from DUKES and TRANSCO (2004) (MJ/m3)
1990
37.97
38.61
1991
37.80
-
Review of Carbon Emission Factors
1992
38.52
-
1993
38.80
-
1994
39.09
38.89
AEA Energy & Environment
1995
39.6
-
1996
39.1
39.27
1997
39.1
-
Page
48
1998
39.1
39.52
1999
39.5
39.76
2000
39.4
39.41
2001
39.8
-
2002
39.8
39.51
2003
39.6
39.5
Appendix 1
=
A1.3
CONVERSION FACTORS FOR GROSS TO NET
ENERGY CONSUMPTION
Table A1.3.1 displays the conversion factors used for Gross to Net Energy
consumption as listed in the UK Greenhouse Gas Inventory 1990-2002,
(Baggott et al, 2004).
Table A1.3.1: Conversion factors for Gross to Net energy consumption
Fuel
Other Gaseous Fuels
Solid and Liquid Fuels
LPG and OPG
Blast Furnace Gas
Review of Carbon Emission Factors
Conversion factor
0.9
0.95
0.92
1.0
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49
Appendix 2
=
Appendix 2
A2.1
REVIEW OF FRACTIONS OF CARBON LEFT
UNOXIDISED AFTER COMBUSTION IN LIQUID
FUELS
Background
Emissions of carbon can be estimated from the quantities of fuel burnt, their carbon contents,
and the fraction of carbon that is not oxidised during the combustion.
The current assumption in the UK Greenhouse Gas inventory is that 100% of the liquid fuels
and gaseous fuels are oxidised. The EU ETS default is 99.5%.
Review
To review the assumptions currently used, we have
contacted the UK Petroleum Industries Association (UKPIA) to seek their view on the
appropriate oxidation factors
considered the views of experts involved in the mobile combustion chapter of the
2006 IPPC guidelines
consulted with our transport sector, Tim Murrells, for his views on the mobile
combustion
Response from UKPIA
From an analysis of data provided by Ian McPherson of UKPIA, Malcolm Watson, UKPIA, has
suggested that for large combustion plant in refineries the carbon oxidation is 99.9%. This
analysis ignores any soot deposited in and around the combustion chamber (JW - but this is
likely to negligible).
Views of authors involved in the 2006 IPCC GLs
A table of oxidation factors were produced for the IPCC 2006 GLs by Kainou Kazanuri from a
range of sources, including the IPCC EF database, and data from the IEA. This covered all
the IPCC fuels.
Jos Olivier (RIVM, Netherlands) makes the point that in general the non-oxidised fraction (i.e.
that remains as particles following combustion) is very small, and is much smaller than the
uncertainty in the emission factors and certainly much smaller than the accuracy of the
activity data. He considers this correction term more of an 'academic' character (i.e. in
principle OK), than of an topic of any significance for accurately estimating CO2 emissions.
Jos recommended to apply values other than 1 in cases where there is a significant fraction
carbon non-oxidised.
Greg Marland (Oak Ridge National Laboratory) notes that there is an analysis within the US
EPA that suggests 100% oxidation of fuel for modern automobiles. Greg notes that he does
not know if this assumption can be extended to the full mobile sector.
View of Tim Murrells (NAEI transport sector expert)
This is an issue we regularly have to consider when calculating fuel consumption and CO2
factors for road transport by specific vehicle types.
When data sources provide fuel consumption factors in g fuel/km for different fuels and types
of vehicles, they actually derive these from measurements of CO2 tailpipe emissions and work
back to calculate fuel consumption from measured tailpipe CO2 emissions and the measured
tailpipe emissions of other carbon containing species CO, hydrocarbons and PM. There are
text-book equations to do this using the carbon contents of these other species. These are
Review of Carbon Emission Factors
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50
Appendix 2
=
based on the assumption that all PM emitted from vehicle exhausts is in the form of elemental
carbon and they assume an average carbon content of the emitted hydrocarbons.
The terminology that is used is 'tailpipe CO2' (the amount of CO2 actually emitted) and
'ultimate CO2', (the amount that has the potential of forming CO2 based on the total amount of
carbon emitted). It is ultimate CO2 that is related to fuel consumption rates.
The actual amount of carbon emitted in forms other than CO2 is time-variable, depending on
the make-up of the fleet. Old petrol cars without three-way catalysts emitted a significant
amount of carbon as CO and hydrocarbons. But with improvements in engines and
abatement technology, this has reduced significantly. Recent test data we have just been
analysing for DfT shows that for modern cars, about 99.4 - 99.7% of carbon is emitted as
CO2 from the tailpipe of petrol cars and 99.6 - 99.9% of carbon is emitted as CO2 from diesel
cars.
This doesn't make any difference to us if it is assumed (as we do) that regardless of what the
carbon is emitted as it has the potential (and will) form CO2 in the atmosphere. For CO and
hydrocarbons that is a fair assumption, but I have never been comfortable with the idea that
emitted PM can potentially form CO2 and to this end I think we ought to subtract the amount
of exhaust PM emitted as carbon (from our calculation of PM emissions) from DUKES fuel
consumption stats.
The 0.3-0.6% of carbon that is not emitted as CO2 from petrol vehicles is virtually all emitted
as CO and HC, so there are no worries here in using the DUKES figures and carbon content
factors as this means all the carbon in the fuel is emitted in a form that will go on to form CO2.
For diesel vehicles, though, a significant amount of the 0.1-0.4% of carbon that is not emitted
as CO2 is emitted as PM, so that ought to be taken into account in the calculations from
DUKES figures on diesel consumption.
Some calculations I've done show that for modern vehicles, <0.01% of carbon in petrol is
emitted as PM and 0.05-0.1% of carbon in diesel is emitted as PM. I should stress though the
figures for diesel are time-varying, as cleaner engines and technologies penetrate the fleet,
the amount of PM emitted is decreasing. In 1990, the allowance for diesel emitted PM in the
carbon calculations will be higher. Also, don't take this figure for diesel as generic - for gas-oil
consumption in diesel trains, machinery, shipping etc, these are less well-designed engines
with no PM abatement, and a more significant fraction of carbon in the diesel consumed by
these engines will be emitted as PM, so a bigger correction in the DUKES figures ought in
theory to be made.
I could develop a "fleet-weighted" correction factor based on diesel PM emissions that can be
applied to the road transport CO2 calculations from DUKES diesel consumption, but it
depends what you intend to do with the information. There could be a tricky issue in that the
PM emissions for road transport are calculated from traffic data and the carbon emissions
being calculated from DUKES figures exclude the contribution of 'fuel tourism' vehicles that
contribute to the UK traffic and therefore contribute to our PM inventory, but not our carbon
inventory.
Recommendation
Our view is that the fraction oxidised for liquid fuels should remain at 100% across the time
series, primarily because of the uncertainty in the estimates of the fractions of fuels
unoxidised and the difficulties of generating an accurate and defensible time series of
unoxidised fractions for each fuel used in the GHG inventory from 1990 to 2004.
Adopting this approach will mean that the base year emissions will be unaffected. This will
result in a slightly conservative estimate of carbon emissions – possibly more so in 1990
where combustion technology was not so advanced and the fraction of carbon unoxidised
would have been slightly greater.
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Appendix 3
=
Appendix 3
A3.1
PROJECT MEETINGS
Date
Meeting
Attendees
01.07.2004
Gas emission factors and calorific
values for use in ETS and NAEI
Jim Penman
Defra
Sayeeda Tauhid
Defra
Caroline Doble Defra
Sarah Baggott Defra/AEAT-netcen
John Watterson AEAT-netcen
Howard Rudd AEAT-FES
David Wilson DTI
Rob Gemmill EA
Dave Lander Transco
Chris Allen
Transco
Phil Pryor
NG Transco
Mike Cunningham
SEPA
Defra, Ashdown House, London
10.08.2004
Natural Gas Calorific Values and
Emission Factors for Use in the
NAEI and the EU ETS
Defra, Ashdown House, London
Review of Carbon Emission Factors
DEFRA – Chris Dodwell, Caroline
Austwick, Sayeeda Tauhid
NETCEN – John Watterson, Sarah
Baggott
FES – Philip Wright
Transco – Dave Lander, Phil Prior
DTI – Margaret Maier, Roger Lampert
EA – Haydn Jones
SEPA – Mike Cunningham, Stephen
Boyle
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